Method of producing molten metal

ABSTRACT

In a method of producing molten metal ( 8 ) from at least partially fine-particulate metal carriers in a melter gasifier ( 2 ) in which under supply of carbon-containing material and oxygen or an oxygen-containing gas under simultaneous formation of a reducing gas in a bed ( 11 ) formed of solid carbon carriers ( 4 ) the metal carriers are melted, the supplied fine-particulate metal carriers in order to avoid discharging thereof are charged to a high-temperature combustion zone ( 13 ) maintained by a combustion process and there are melted at least for the most part or completely, wherein the high-temperature combustion zone ( 13 ) is spatially isolated from the freeboard ( 12 ) of the melter gasifier ( 2 ) located above the bed ( 11 ) and extends into the bed ( 11 ), wherein the offgases formed in the high-temperature combustion zone ( 13 ) exit the same passing through at least a portion of the bed ( 11 ) and wherein furthermore the offgases are cooled in the bed ( 11 ) and are withdrawn from the melter gasifier ( 2 ) along with the reducing gas formed within the bed ( 11 ).

[0001] The invention relates to a method of producing molten metal, inparticular pig iron or steel pre-products, from at least partiallyfine-particulate metal carriers, in particular partially reduced orreduced sponge iron, in a melter gasifier in which under supply ofcarbon-containing material and oxygen or an oxygen-containing gas undersimultaneous formation of a reducing gas in a bed formed of solid carboncarriers the metal carriers are melted, optionally upon previouscomplete reduction, as well as to a melter gasifier for carrying out themethod.

[0002] From EP-B-0 010 627 it is known to feed in particulateiron-containing material, such as pre-reduced sponge iron, through acentrally arranged charging opening in the hood of the melter gasifierfrom above, with the particles dropping into the melter gasifier by theeffect of gravity and being slowed down in the fluidized bed existingwithin the melter gasifier. Coal in lumpy form is charged through acharging opening arranged laterally in the hood of the melter gasifieror in the dome terminating the melter gasifier toward the top, alsounder the influence of gravity. The reducing gas formed in the meltergasifier is withdrawn through the centrally arranged charging openingfor the iron-containing material.

[0003] A process of this kind is not suitable for processingfine-particle metal carriers, in particular fine-particle sponge iron,since the fine-particle metal carriers due to the pronounced gas flow ofthe reducing gas formed in the gasification zone and withdrawn throughthe central charging opening arranged in the hood or in the dome of themelter gasifier would be instantly carried out of the melter gasifier.Such a discharge of the fine-particle metal carriers is further favoredby the temperature reigning in the upper region of the melter gasifier,i.e. in the region above the gasification zone, which is too low toensure a melt-down, i.e. agglomeration of the fine particles at thecharging site to form bigger particles which in spite of the ascendinggas stream could sink down into the gasification zone.

[0004] From EP-A-0 217 331 it is known to introduce pre-reduced fine oreinto a melter gasifier and to completely reduce and melt it by means ofa plasma burner while supplying a carbon-containing reducing agent. Thepre-reduced fine ore or the sponge-iron powder respectively is fed to aplasma burner provided in the lower section of the melter gasifier. Adisadvantage of this method is that by supplying the pre-reduced fineore directly in the lower meltdown region, i.e. in the region where themelt collects, complete reduction can no longer be ensured and thechemical composition necessary for further processing the pig ironcannot be achieved by any means. Moreover, the charging of major amountsof pre-reduced fine ore is not feasible due to fluidized bed or thefixed bed forming from coal in the lower region of the melter gasifier,as it is not possible to carry off a sufficient quantity of the meltingproducts from the high-temperature zone of the plasma burner. Thecharging of major amounts of pre-reduced fine ore would lead to instantthermal and mechanical failure of the plasma burner.

[0005] From EP-B-0 111 176 it is known to feed a fine grain fraction ofsponge iron particles into the melter gasifier through a downpipeprojecting from the head of the melter gasifier into the proximity ofthe coal fluidized bed. At the end of the downpipe a baffle plate isprovided for minimizing the velocity of the fine grain fraction,resulting in a very low exit velocity of the fine grain fraction fromthe downpipe. At the charging site, the temperature reigning in themelter gasifier is very low, whereby immediate melting of the suppliedfine grain fraction is prevented. This and the low exit velocity fromthe downpipe cause a substantial portion of the supplied fine grainfraction to be carried out of the melter gasifier again together withthe reducing gas generated in the same. The charging of a major amountof sponge iron particles containing a fine portion or of only a finegrain fraction is not feasible in accordance with this method.

[0006] From EP-A-0,594,557 it is known to charge a fine grain fractionof sponge iron by means of a conveying gas directly into the fluidizedbed formed by the gasification zone in the melter gasifier. However,this is disadvantageous, since hereby the gas circulation of thefluidized bed may be disturbed because obstructions of the fluidizedbed, which acts like a filter, may ensue as a consequence of the finegrain fraction that is blown directly into the fluidized bed. As aresult, eruptive outbreaks of gas may occur which will break up theclogged fluidized bed. Hereby, the gasification process for the carboncarriers and also the melt-down process for the reduced iron ore aremarkedly disturbed.

[0007] From EP-A-0 576 414 it is known to feed fine-particle metalcarriers into the gasification zone via dust burners. This methodexhibits a poor melt-in performance, which is due to a short dwellingtime of the particles in the hot flame.

[0008] The invention aims at avoiding these disadvantages anddifficulties and has as its object to provide a method of the kindinitially described as well as a melter gasifier for carrying out themethod, allowing the processing of fine-particulate metal carrierswithout the need for briquetting and, in doing so, on the one hand toreliably avoid discharging of the supplied fine-particulate metalcarriers, optionally in pre-reduced or in completely reduced condition,by the reducing gas produced in the melter gasifier, and on the otherhand to ensure complete reduction, which may optionally be required, ofthe fine particles. It is a particular object of the invention toprovide a method enabling the processing of a charge the greatest part,preferably 100%, of which is/are made up of fine-particulateiron-containing material to pig iron and/or steel prematerial utilizinga melter gasifier.

[0009] With a method of the initially described kind, this object isachieved in that the fine-particulate metal carriers are charged to ahigh-temperature combustion zone maintained by a combustion process andthere, optionally upon complete reduction, are melted at least for themost part or completely, wherein the high-temperature combustion zone isspatially isolated from the freeboard of the melter gasifier locatedabove the bed and extends into the bed, wherin the offgases formed inthe high-temperature combustion zone exit the same passing through atleast a portion of the bed and wherein furthermore the offgases arecooled in the bed and are withdrawn from the melter gasifier along withthe reducing gas formed within the bed.

[0010] A melter gasifier for carrying out the method, having feed ductsfor oxygen-containing gases, carbon carriers and metal carriers runninginto it and having at least one gas discharge duct for a reducing gasproduced in a bed of the melter gasifier formed of solid carbon carriersdeparting from it, and with a tap for the metal melt and for slag ischaracterized in that at least one feed duct for feedingfine-particulate metal carriers opens into at least one high-temperaturecombustion chamber that is spatially isolated from the interior of themelter gasifier and, by a mouth, in turn projects into the bed formed ofsolid carbon carriers and is provided with a burner.

[0011] To assure easy access to the high-temperature combustion chamberas well as a long service life of the same, the high-temperaturecombustion chamber is advantageously constructed as a wall that departsfrom the dome of the melter gasifier, is open at the bottom, cylindricalin shape and provided with a refractory material.

[0012] A simple construction is characterized in that only a singlehigh-temperature combustion chamber is provided which is arrangedcentrally and with its longitudinal axis lying in the verticallongitudinal axis of the melter gasifier.

[0013] Advantageously, the high-temperature combustion chamber by itsupper end projects outward through the dome of the melter gasifier andat this exterior end the feed duct for fine-particulate metal carriersruns into the high-temperature combustion chamber, and furthermore theburner is arranged centrally at this outer end, whereby repair work tobe done on the burner or exchange of the same is feasible in an easymanner.

[0014] An ideal structure of the bed is attainable if according to apreferred embodiment feed ducts for carbon carriers project into themelter gasifier at a radial distance from the high-temperaturecombustion chamber, into the dome of the melter gasifier.

[0015] The service life can be further increased if the wall of thehigh-temperature combustion chamber is provided with an internal wallcooling, wherein advantageously the wall of the high-temperaturecombustion chamber is equipped with finned tubes which are flown throughby a cooling medium and are provided with a refractory lining on bothsides, and, further, at the upper end and at the lower end of thehigh-temperature combustion chamber there are suitably providedring-shaped headers for a cooling medium, preferably cooling water, eachbeing integrated into the wall of the high-temperature combustionchamber.

[0016] At its end projecting outward through the dome of the meltergasifier, the high-temperature combustion chamber suitably is providedwith a removable cover and the burner and the feed duct are arranged inthe cover.

[0017] It is beneficial to the process course if the burner is formed bya fine-coal/oxygen burner.

[0018] In the following, the invention is explained in more detail withreference to an exemplary embodiment represented in the drawing, whereinthe FIGURE illustrates a melter gasifier in vertical longitudinalsection in schematic representation.

[0019] Pre- or completely reduced fine ore—in case of iron-containingfine ore this will be sponge iron powder—is supplied to a meltergasifier 2 through at least one conveying duct 1 in a manner that willbe described in more detail below. In the melter gasifier 2, a CO—andH₂—containing reducing gas is produced from coal 4 and oxygen-containinggas in a gasification zone 3 and is fed for example into a fluidized bedreactor (not illustrated) via a reducing-gas discharge duct 5. Thereducing gas streams through this fluidized bed reactor in counterflowto the ore flow in order to reduce fine-particulateiron-oxide-containing material and is discharged from the fluidized bedreactor via a top-gas discharge duct, is subsequently cooled andscrubbed in a wet scrubber and then is available to consumers as a topgas.

[0020] The melter gasifier 2 is provided with supply ducts 6 for solidcarbon carriers in lumpy form, supply ducts 7 for oxygen-containinggases as well as optionally supply ducts for carbon carriers, such ashydrocarbons, that are liquid or gaseous at room temperature as well asfor burned fluxes.

[0021] In the melter gasifier 2, in a lower section I below thegasification zone 4, molten pig iron 8 or molten steel pre-materialrespectively and molten slag 9 collect, which are tapped off via a tap10.

[0022] In a section II of the melter gasifier 2 arranged above the lowersection I a bed 11 is formed from the solid carbon carriers, preferablya fixed bed and/or a fluidized bed. The upper section III provided abovethe central section II serves as a calming space 12 for the reducing gasforming in the melter gasifier 2 and for solid particles entrained bythe reducing gas.

[0023] The pre- or completely reduced fine ore is charged into thegasification zone 3 via a high-temperature combustion zone 13 arrangedvertically and centrally in the melter gasifier 2, into which zone thereenters the conveying duct 1—by several branch ducts. Thehigh-temperature combustion zone 13 is provided in a high-temperaturecombustion chamber 14 penetrating the dome of the melter gasifier 2 andprojecting downward into the bed 11. It is constructed so as to becylindrical and open at the bottom and is provided with a wall 15designed to be refractory.

[0024] The high-temperature combustion chamber 14 is at its upper endprovided with a removable cover 16 through which the conveying duct 1with the branch ducts is conducted. Centrally in the cover 16, a burner17, preferably a fine-coal/oxygen burner, is arranged whose flame jet isdirected vertically downward.

[0025] The wall 15 of the high-temperature combustion chamber 14 isprovided with an internal wall cooling formed by finned tubes 18 whichare flown through by a cooling medium. On both sides of the finned tubes18, a refractory lining 19 is arranged. At the upper end and at thelower end of the high-temperature combustion chamber 14, ring-shapedheaders 20 for the cooling medium, preferably cooling water, arearranged, each being integrated into the wall 15 of the high-temperaturecombustion chamber 14.

[0026] The feed ducts 6 for the solid lumpy carbon carriers projectthrough the dome 21 of the melter gasifier 2 at a radial distanceoutside of the high-temperature combustion chamber 14. As can be seenfrom the FIGURE, the bed 11 will form radially outside of thehigh-temperature combustion chamber 14, in a ring-like shape. Below thehigh-temperature combustion chamber 14 there will form a cavern 22 ofroughly conical shape.

[0027] In the high-temperature zone 13 maintained by means of the burner17, the sponge iron powder is melted for the major part, preferablyentirely, and it enters the bed 11 or the combustion zone 3,respectively, in liquid condition. The melted sponge iron tricklesdownward through the coke network that forms the bed 11 and iscarburized in the process. The hot offgases originating in thehigh-temperature combustion zone 13 enter the bed 11 from thecone-shaped zone that is free from piled-up material, i,e. thecone-shaped cavern 22, and together with the reducing gas formed in thegasification zone 3 flow upwards via the annular bed radially adjacentthe combustion chamber 14 and are carried off via the reducing-gasdischarge ducts 4. In flowing through the bed 11, the offgases cool downto the desired offgas temperature of roughly 1000° C.

[0028] In accordance with the invention, melting thus takes placeentirely or at least almost entirely above the bed 11, whereby theresidence time of the sponge iron in the melter gasifier 2 isconsiderably increased. Furthermore, discharging of sponge iron powderfrom the melter gasifier 2 is no longer possible, since the sponge ironpowder is supplied directly to the bed 11 in the downward direction,with the offgases formed in the high-temperature combustion zone 13.Here, melt droplets are filtered off from the offgases by means of thebed 11, so that the operation of the melter gasifier 2 is markedlyenhanced as compared with the prior art.

[0029] The invention is not limited to the illustrated exemplaryembodiment but may be modified in various respects. In particular,utilization for metals other than iron, especially copper (oxidic,sulfidic), tin, lead (metallic, oxidic or sulfidic), nickel andchromium—the last two in the form of ore—has to be considered. It isalso feasible to charge a portion of the sponge iron to the bed 11 inlumpy form, f.i. as pellets, namely outside of the high-temperaturecombustion zone 13, the zone 3 thus having to be denoted not just as agasification zone but also as a melt-down gasifying zone.

[0030] Utilization for oxidic charging substances, such as f.i.unreduced iron oxide or oxidic copper, tin, lead, is energeticallyfeasible. In that case, a prereduction and a complete reduction wouldtake place in the high-temperature zone, supply of oxygen and coalhaving to be increased.

1. Method of producing molten metal, in particular pig iron (8) or steelpre-products, from at least partially fine-particulate metal carriers,in particular partially reduced or reduced sponge iron, in a meltergasifier (2) in which under supply of carbon-containing material (4) andoxygen or an oxygen-containing gas under simultaneous formation of areducing gas in a bed (11) formed of solid carbon carriers (4) the metalcarriers are melted, optionally upon previous complete reduction,characterized in that the fine-particulate metal carriers are charged toa high-temperature combustion zone (13) maintained by a combustionprocess and there, optionally upon complete reduction, are melted atleast for the most part or completely, wherein the high-temperaturecombustion zone (13) is spatially isolated from the freeboard (12) ofthe melter gasifier (2) located above the bed (11) and extends into thebed (11), wherein the offgases formed in the high-temperature combustionzone (13) exit the same passing through at least a portion of the bed(11) and wherein furthermore the offgases are cooled in the bed (11) andare withdrawn from the melter gasifier (2) along with the reducing gasformed within the bed (11).
 2. Melter gasifier (2) for carrying out themethod according to claim 1 for producing a metal melt, preferably a pigiron melt (8), from at least partially reduced metal carriers, inparticular sponge iron, containing a portion of fine-particulate metalcarriers, and for producing a reducing gas by coal gasification, saidmelter gasifier (2) having feed ducts (1, 6, 7) for metal carriers,carbon carriers and oxygen-containing gases running into it and havingat least one gas discharge duct (5) for a reducing gas produced in a bed(1l) of the melter gasifier (2) formed of solid carbon carriers (4)departing from it, and with a tap (10) for the metal melt (8) and forslag (9), characterized in that at least one feed duct (1) for feedingfine-particulate metal carriers opens into at least one high-temperaturecombustion chamber (14) that is spatially isolated from the interior(12) of the melter gasifier (2) and, by a mouth, in turn projects intothe bed (11) formed of solid carbon carriers (4) and is provided with aburner (17).
 3. Melter gasifier according to claim 2, characterized inthat the high-temperature combustion chamber (14) is constructed as awall (15) that departs from the dome (21) of the melter gasifier (2), isopen at the bottom, cylindrical in shape and provided with a refractorymaterial (19).
 4. Melter gasifier according to claim 3, characterized inthat only a single high-temperature combustion chamber (14) is providedwhich is arranged centrally and with its longitudinal axis lying in thevertical longitudinal axis of the melter gasifier (2).
 5. Meltergasifier according to claim 3 or 4, characterized in that thehigh-temperature combustion chamber (14) by its upper end projectsoutward through the dome (21) of the melter gasifier (2) and that atthis exterior end the feed duct (1) for fine-particulate metal carriersruns into the high-temperature combustion chamber (14), and thatfurthermore the burner (17) is arranged centrally at this outer end. 6.Melter gasifier according to one or several of claims 3 to 5,characterized in that feed ducts (6) for carbon carriers project intothe melter gasifier (2) at a radial distance from the high-temperaturecombustion chamber (14), into the dome (21) of the melter gasifier (2).7. Melter gasifier according to one or several of claims 2 to 6,characterized in that the wall (15) of the high-temperature combustionchamber (14) is provided with an internal wall cooling.
 8. Meltergasifier according to claim 7, characterized in that the wall (15) ofthe high-temperature combustion chamber (14) is equipped with finnedtubes (18) which are flown through by a cooling medium and are providedwith a refractory lining (19) on both sides.
 9. Melter gasifieraccording to claim 8, characterized in that at the upper end and at thelower end of the high-temperature combustion chamber (14) there areprovided ring-shaped headers (20) for a cooling medium, preferablycooling water, each being integrated into the wall (15) of thehigh-temperature combustion chamber (14).
 10. Melter gasifier accordingto one or several of claims 2 to 9, characterized in that at its endprojecting outward through the dome (21) of the melter gasifier (2) thehigh-temperature combustion chamber (14) is provided with a removablecover (16) and that the burner (17) and the feed duct (1) are arrangedin the cover (16).
 11. Melter gasifier according to one or several ofclaims 2 to 10, characterized in that the burner (17) is formed by afine-coal/oxygen burner.